math
posted by Kate .
Two trucks left buck's trucks traveling in opposite directions. One truck traveled at a rate of 70km/h, the other at 80km/h. After how many hours were the trucks 900km apart?
I got 3 hours as my answer, but I don't think that's right...

Never minds. I see my mistake. It's really 6 hours.

You could easily check your answer.
first truck went 3(70) or 210 km
2nd truck went 3(80) = 240 km
nope, that does not add up to 900, so
let the time be t hours
70t + 80t = 900
150t = 900
t = 6
I will leave it up to you to check my answer. 
thanks. I though because you added 70t and 80t there would be 2ts. But no.